The production of organic compounds using carbon monoxide or synthesis gas, which is a mixture of carbon monoxide and hydrogen, as a reactant has been known for a significant period of time. It is well known that one can produce methanol directly from synthesis gas and that methanol can be further reacted by hydroformylation, homologation and carbonylation reactions to produce acetaldehyde, ethanol and acetic acid or its methyl ester, respectively. It is also known that esters, ethers, and other organic compounds can be reacted with carbon monoxide or synthesis gas to produce oxygenated organic compounds. The difficulties, however, have resided in the ability to carry out any one of these chosen reactions to produce the desired compound at acceptable efficiency, conversion rate and selectivity.
In almost all instances the reaction is generally catalyzed using a Group VIII transition metal compound as catalyst and a hologen as the promoter. It is known that many other metal compounds and promoters can be used. In addition, the prior art has disclosed the use of secondary activators or ligands in conjunction with the metal catalysts and promoters. These secondary activators can be other metallic salts or compounds, amines, phosphorus compounds, as well as a multitude of other compounds that have been disclosed in the published literature. Thus, a typical catalyst system contains the metal atom catalyst, promoter and, optionally, ligands, solvents and secondary activators. Though a significant amount of literature does exist describing the production of oxygenated organic compounds by the reaction of esters or alcohols with carbon monoxide or synthesis gas, to our knowledge it does not disclose or suggest our improved invention. Several of the pertinent patents in this area are discussed below.
In U.S. Pat. No. 3,356,734, issued to Kuraishi et al on Dec. 5, 1967, there is disclosed a process for producing acetaldehyde by the reaction of methanol with synthesis gas using a cobalt catalyst promoted by a halogen promoter. It contains no recognition of the benefits to be achieved with specific halogen promoters, nor does it suggest or disclose the use of initial reactants other than methanol.
The production of esters by the reaction of esters or ethers with synthesis gas is the subject of U.S. Pat. No. 4,189,441, issued to Braca et. al. on Feb. 19, 1980. The reaction is carried out using a ruthenium carbonyl and halogen promoter system. There is no specific mention of lithium iodide and there is obtained a mixture of many products; the reaction is not selective and aldehydes were not observed. In related articles, J. Am. Chem. Soc., 1978, 100, 6238, and Fundamental Research of Homogeneous Catalysis, Vol. 3, Plenum (1979), Braca et al state that no acetaldehyde was found among the products.
On Sept. 30, 1980, U.S. Pat. No. 4,225,517 was issued to Gane. This patent claims a process for reacting methanol with synthesis gas for the production of acetaldehyde in the presence of a cobalt catalyst, an iodine or bromine promoter, a compound of one of the elements arsenic, antimony or bismuth and the additional presence of an additive which can be an inert liquid, or an acid or acid derivative, or an oxygen-containing compound, or a non-polar solvent. The selectivities reported are below 60%. The patent contains no recognition of the unexpected and unpredictable benefits to be achieved by any single specific halogen compound. In column 10, lines 5 and 6, Gane indicates that the use of a trivalent phosphorus compound resulted in the production of ethanol as the major product rather than the production of acetaldehyde.
The Pretzer et. al. patent, U.S. Pat. No. 4,239,704, issued on Dec. 16, 1980, discloses a process for producing acetaldehyde by the reaction of methanol with synthesis gas using a system containing a cobalt entity, a ligand and an iodine compound. The reaction is non-selective, producing a mixture of many products, and exhibits a low selectivity to acetaldehyde and a relatively low conversion rate. Among the sources of halogen atom availability, lithium iodide is mentioned at column 4, line 24.
The reaction of methyl acetate with synthesis gas to produce acetic anydride is shown in U.S. Pat. No. 4,251,458, issued Feb. 17, 1981 to J. Pugach using a Group VIII noble metal component with a halogen component and an arsenic component. Though alkali metal halides are mentioned, there is no data supporting production of acetaldehyde. Nor does the patent contain any recognition of the benefits to be achieved by any specific halogen composition.
In Japanese Publications Nos. 77/136110, and 77/136111, filed by Saito et al and published on Nov. 14, 1977, there are disclosed cobalt catalysts promoted with an iodine compound and employing a phosphorus compound to react methanol with synthesis gas to produce acetaldehyde. In neither publication is there any mention of lithium iodide and both show low selectivities.
Japanese Publication No. 77/133914, filed by Saito et al and published on Nov. 9, 1977, relates to the reaction of methanol with synthesis gas to produce acetaldehydes using a system containing cobalt, a halide promoter and at least one element of the group, arsenic, antimony and bismuth. There is no disclosure of advantages to be gained from any specific halogen component and selectivities were low.
U.K. Patent Application No. 2,001,070A, filed by A. Saus and published on Jan. 24, 1979, relates to the homologation of esters with synthesis gas to produce a higher homolog of the charged ester. The catalyst system contains at least one of the metals cobalt, rhodium, ruthenium or iron and an iodine promoter. There is no suggestion or disclosure of the unexpected results to be achieved using lithium iodide.
The preparation of acetaldehyde by the reaction of methyl acetate with synthesis gas is the subject of U.K. patent application No. 2,038,829A filed by R. V. Porcelli and published on July 30, 1980. The catalyst system contains palladium, an iodine moiety (preferably methyl iodide), an organic promoter containing nitrogen, phosphorus, arsenic or antimony, and/or an inorganic promoter of elements having an atomic weight greater than 5 of Groups IA, IIA, IIIA, IVB, VIB and the non-noble metals of Group VIII. The reaction requires the use of the expensive palladium and excessive amounts of methyl iodide, a compound which is considered highly corrosive and thus very undesirable.
European Patent Application No. 0,025,702, published Mar. 25, 1981 and filed by Isshiki et al., pertains to the conversion of methyl acetate or dimethy ether to ethylidenediacetate using a system containing a nickel or cobalt compound and an iodine or bromine compound in conjunction with a promoter. Though LiI is disclosed as a suitable halide, it is not used in any of the examples, nor is there any suggestion or recognition of the unexpected results to be achieved by its use in the production of acetaldehyde from methyl acetate.
European Patent Application No. 0,031,784, published July 8, 1981, and filed by Gauthier-Lafaye et al., discloses a process for the homologation of esters to the next higher homolog. The catalyst system contains cobalt, ruthenium and iodine moieties; a combination of ionic and covalent halide is charged. A trace amount of acetaldehyde is reportedly produced as a by-product.
In German Offenlegungsschrift DE No. 2,941,232 Al, filed by Hans-Klaus et al., and published on Apr. 23, 1981, methyl acetate is reacted with synthesis gas using a system containing rhodium in combination with rhenium, manganese, or ruthenium, halogen compound, aliphatic carboxylic acid and a heterocycllic aromatic compound having a quarternary nitrogen atom. The principal product obtained was ethylidenediacetate; there is no indication that acetaldehyde could be made.
It can be seen that the prior art contains many disclosures dealing with the catalytic production of aldehydes via the reaction of alcohols and ethers with synthesis gas. In the reaction of an alcohol the accepted net reaction is: EQU ROH+CO+H.sub.2 .fwdarw.RCHO+H.sub.2 O
One of the disadvantages in many of these references is the formation of water with the eventual need to remove it from the desired organic product. This removal is both complicated and costly. Other disadvantages often include the simultaneous occurrence of other reactions leading to the formation of by- products, such as, dimethyl acetal, methyl acetate, ethanol, etc. These reactions compete with the acetaldehyde production resulting in low acetaldehyde rate and selectivity.
Many processes employed for the production of aldehydes in the first stage and alcohols in the second reaction stage involve the reaction of an aldehyde with synthesis gas or carbon monoxide using a catalyst system containing a source of ruthenium and a source of halide present at least during the first stage. The alkali metal halides are often mentioned as suitable halide sources, but no distinction is made between any specific one of the alkali metal halides or between any other halogen compound. As with the use of methanol as the starting material, the use of formaldehyde also results in the formation of a mole of water, which must subsequently be removed. The formaldehyde-synthesis gas reaction can be shown as: EQU HCHO+CO+H.sub.2 .fwdarw.CH.sub.3 CHO+H.sub.2 O